1. Field of the Invention
The present invention relates to an X-ray diagnostics installation with spatial frequency high-pass filtering, and in particular to such a diagnostics installation having first and second memories and a difference stage for producing subtraction images from successive video signals.
2. Description of the Prior Art
An X-ray diagnostics installation is known from German Pat. No. 12 24 352, corresponding to British specification No. 1,128,852, having spatial frequency high-pass filtering and having first and second memories in which chronologically successive video signals are stored, and a difference stage for producing subtraction images from the signals stored in the memory. The subtraction images displayed on a monitor of this type of X-ray diagnostics installation are particularly suited for enhancing fine contrasts in X-ray pictures. This known system has a video high-pass filter making use of a camera tube as a storage means. The filter is disposed in the transmission channel of the system. As a result, large-area contrast regions are attenuated, whereas the high frequency signal components, which represent the fine contrasts, are intensified. The current video signal is subtracted from the filtered signal or the difference signal by two differencing stages. The degree of enhancement is set by an adjustable amplifier. An intensification of the fine contrasts in this known system is, however, noticeably limited due to inteference structures of the transmission components, for example, due to interference structures of the input luminescent screen or the semiconductor layer of the camera tube.